Bacillus anthracis is a gram-positive, spore-forming bacterium that causes anthrax in humans and other mammals. Because of the high resilience of B. anthracis spores to extremes of their environment they can persist for many years until encountering a signal to germinate. When spores of B. anthracis are inhaled or ingested they may germinate and establish populations of vegetative cells which release anthrax toxins often resulting in the death of the host. The relative ease by which B. anthracis may be weaponized and the difficulty in early recognition of inhalation anthrax due to the non-specific nature of its symptoms were demonstrated by the death of four people who inhaled spores from contaminated mail (Jernigan et al., 2002, Emerg Infect Dis; 8:1019-1028; Jernigan et al., 2001, Emerg Infect Dis; 7:933-944; Webb, 2003, Proc Natl Acad Sci; 100:4355-4356). Consequently, considerable efforts are being directed towards the development of early disease diagnostics and improved anthrax vaccines.
B. anthracis belongs to the Bacillus cereus group which includes the closely related B. cereus, B. anthracis, and B. thuringiensis species. Bacillus cereus strains can be potent food-borne pathogens, while B. thuringiensis are insect pathogens, and B. anthracis is the causative organism of anthrax. Although differentiation amongst B. cereus, B. thuringiensis and B. anthracis in practice is not difficult, the speed and specificity of confirmatory identification of virulent B. anthracis are of great importance in the context of bioterrorism preparedness and emergency response. This need is all the more pressing as the existence of non-pathogenic B. anthracis strains is well established and recent studies have shown the potential for B. cereus strains to harbor functional B. anthracis virulence genes (Hoffmaster et al., 2004, Proc Natl Acad Sci 101:8449-8454).
Thus, there is a need for improved diagnostic assays that can reliably identify anthrax in its early stages and quickly distinguish it from other flu-like or febrile illnesses. And, in view of the potential use of B. anthracis as a weapon in a bioterrorism attack, there is a need for improved vaccines.